Older blog entries for dgh (starting at number 11)

D-Bus API in DevHelp

The Telepathy API has until recently only been available as a single large HTML document. The HTML is generated from D-Bus introspection XML with extensions for stuff like enums. I hacked up a conversion to DevHelp's index format, meaning you can use DevHelp to browse the documentation.

To set it up:

  • check out the telepathy-spec repository
  • run make
  • copy doc/spec.html and doc/telepathy-spec.devhelp2 to a directory /usr/share/doc/gtk-doc/html/telepathy-spec/

This might also work for other D-Bus APIs; I haven't tried.

(If you're developing using Gtk/GLib/Cairo/Pango/GStreamer/etc. and not tried DevHelp, I heartily recommend it. It's really handy, especially with the Ctrl-S shortcut.)

Syndicated 2007-09-22 15:16:28 (Updated 2007-09-22 15:16:56) from Dafydd

Bike power

Recently I got involved with a local group, the Magnificent Revolutionary Cycling Cinema. The idea is to use bikes to generate electricity, and to use that as an instrument for education, in particular about sustainability. We just had our first outing at The Big Chill, a three-day music festival.

Eight of us cycled from Cambridge to the Big Chill site in Herefordshire, a journey of roughly 130 miles. Many others arrived by other means to take part. Once we got there, we set up a tent with a platform for the bikes, a central console for managing the power generation, a projector and a pair of speakers. This took the best part of a week.

By some amazing coincidences, many people with ties to the project happened to be at the festival:

  • David Butcher, the godfather of pedal power; who was doing his own bike-powered project at the festival
  • members of the Chicago and local Ross-on-Wye chapters of the Rat Patrol, who brought along some brilliant mutant bikes and home brew cider
  • Fredric King, producer of B.I.K.E., a film we were showing about the Black Label Bicycle Club
  • Run Wrake, creator of amazing short film Rabbit that we were also showing; though Run was VJing at the Big Chill, we sadly didn't get to meet him

As for the cinema: in general, reception was very positive. Many festivalgoers made the trek up the hill from the festival to visit us, and people were generally keen to get on a bike for a bit and feed our machine. We were very happy that it all actually worked; as it turns out the power we generated was pretty close to what we needed to keep running. (Odd, and somewhat disquieting, to think that the tent housing our roughly 330 Watt show was shone upon by a number of 1000 Watt lights.)

By the end, we were all exhausted from the 10pm-3am shifts, and somewhat sad at having to take it all apart. Nevertheless, I had a wonderful time. We learned a lot from our first excursion, and got lots of ideas for future improvements. Everyone involved seems eager to take the project forward to further success.

Syndicated 2007-08-12 03:34:57 (Updated 2007-08-12 03:42:19) from Dafydd


Though it's been a while since Guadec, it's been a rather busy time since so I've only just got around to putting up the photos I took there. Shortly after getting to Birmingham, I gave in to the temptation of a 30mm f/1.4 Sigma lens. Guadec was great for testing it on people.

Syndicated 2007-08-11 18:34:01 from Dafydd

party: July 13th

Matthew Garrett has a birthday soon. As birthday is a pretty good excuse to have people come to your house and drink. So, if you're in Cambridge on July 13th, come to 6b Fair Street with some booze or food around 9pm, and help Matthew forget how old he is.

Syndicated 2007-07-08 11:57:48 from Dafydd

a difficulty in criticising Wikipedia

When people criticise Wikipedia, they often cite specific errors in articles as evidence that its overall quality is poor. The irony in this is that it encourages Wikipedians to fix those exact errors.

For instance, in his essay “The Faith-Based Encyclopedia”, Robert McHenry ― one of Wikipedia's most ardent critics ― pointed out ambiguities in the article on Alexander Hamilton:

While the day and month of Hamilton's birth are known, there is some uncertainty as to the year, whether it be 1755 or 1757. Hamilton himself used, and most contemporary biographers prefer, the latter year; a reference work ought at least to note the issue. The Wikipedia article on Hamilton (as of November 4, 2004) uses the 1755 date without comment. Unfortunately, a couple of references within the body of the article that mention his age in certain years are clearly derived from a source that used the 1757 date, creating an internal inconsistency that the reader has no means to resolve.

I think McHenry underestimates Wikipedia's readers, and I suspect that when people notice inconsistencies they are smart enough to refer to other sources. At any rate, the article now devotes an entire paragraph to the question, including two citations. McHenry acknowledges this problem in a later essay (while criticising a different article):

By the time you read this, the entry will likely have been corrected, and some Wikipedians will proclaim this as another proof of concept. It does not occur to them to wonder how many people may have come upon that entry in the more than three years it has existed and relied in some way on the misinformation in it. They nearly got me.

He was right about one thing: the error in the article was fixed that same day. But I think this says something positive about Wikipedia: that it is willing to acknowledge mistakes and try to fix them as soon as they are discovered. For as long as McHenry continues to points out errors, there will be Wikipedians on hand happy to fix them.

Syndicated 2007-07-05 00:08:54 from Dafydd


I am vegetarian. I am also indecisive. Because most restaurants have a small (non-zero) number of vegetarian options, these things go well together. This doesn't work in vegetarian restaurants, which is a shame, because I like to support vegetarian restaurants but I don't like to be faced with many choices.

Syndicated 2007-06-22 12:08:51 from Dafydd

Building tubes

Part of the One Laptop Per Child vision is that children can use the laptop in a very social way. Bringing this vision about involves making it very easy for programs on the laptop (activities in OLPC parlance) to talk to each other. When Collabora was handed the challenge of making this happen, it fit well with an an idea that had been floating around for a while: namely Application Data Channels, a Telepathy interface for sending arbitrary data to your contacts.

While designing a solution for OLPC, we adopted two key simplifications. Firstly, we decided to reuse D-Bus's nice data marshalling and method/signal model, since Telepathy applications will be using D-Bus anyway. Secondly, we dropped the somewhat unwieldy "Application Data Channels" name in favour of calling it tubes.

Last year, Mads Olesen worked on a Google Summer of Code project to introduce Application Data Channels to Jabber. By building on Mads' work, Guillaume laid the groundwork for Jabber tubes in Telepathy. Then, with a bit of libdbus hacking, I got our first tube hooked up.

Since then, we've built an OLPC activity that uses tubes to implement networked board game, Marc Maurer has started on an AbiCollab backend for tubes, and work has begun in Sugar on making tubes really easy for activities to use.

In short: opening a Telepathy tube tube gives you a way to talk D-Bus over the network, without worrying about the underlying protocol. I'm really excited about the sort of things that people will build with this, in OLPC and beyond.

Image © flickr user swafo; licence cc 2.0 by-nc-nd.

Syndicated 2007-05-10 17:39:41 (Updated 2007-05-10 19:45:01) from Dafydd


On Friday, I went to see Punchdrunk's adaptation of Goethe's Faust to 1950s USA; possibly my favourite theatre experience ever. (Previously I would probably have cited Beautiful Thing.) Despite having had only 4 hours' sleep, I had a wonderful wonderful time.

This was no ordinary production:

  • it took place in a disused warehouse in London docklands

  • there are five floors with around 40 rooms

  • audience members wear a mask at all times

  • different parts of the plot happen in parallel

  • you are free to wander around as you please

The sets were detailed and fabulous and at times surreal: an alchemical laboratory, a pine forest, several bars, a diner, a corn field, an office, motel rooms, a family drawing room. At several points, audience members were pulled into the fray. At several points, I became part of a crowd of people running after an actor to follow the story. My role as an audience member was directly challenged, to the extent that my place in the world felt different when I came out.

A few mentions I found from the Grauniad which do it better justice than I are listed here.

My only regrets are that I spent more time than I would have liked searching for the action; and that the run, which ends on the 31st, is completely sold out so that I can't see it again. Nevertheless, I'll be keeping an eye out for future Punchdrunk productions; I hear tell that they have something new starting in September.

Syndicated 2007-03-25 18:14:05 from Dafydd


When I was last in hospital, some tests needed running on my blood. I wasn't overly excited about this, but when the doctor told me that a phlebotomist would be with me shortly to take my sample, the loveliness of the word did much to distract me from my discomfort.

Of course, at the time I did not reflect on how near in sound are "phlebotomy" and "lobotomy".

Syndicated 2007-03-09 00:03:13 from Dafydd

dgh @ 2007-02-15T02:17:00

Tonight I saw Attila the Stockbroker and David Rovics at the Loft: both of them informed, topical, policial, angry, wonderful. There was a lot of joining in on the choruses, especially on songs like Burn it Down, I'm a Better Anarchist than You and Guy Fawkes' Table. I can't resist quoting from Attila's Asylum Seeking Daleks: it captures so well my feelings re Daily Mail xenophobia.

Asylum seeking Daleks
are landing here at noon!
Why can't we simply send them back
or stick them on the moon?
It says here in the Daily Mail
they're coming here to stay -
The Loony Lefties let them in!
The middle class will pay...

This satire on crass ignorance
and tabloid-fostered fear
Is at an end. Now let me give
One message, loud and clear.
Golf course, shop floor or BNP:
Smash bigotry and hate!
Asylum seekers - welcome here.
You racists: emigrate!

Syndicated 2007-02-15 02:34:17 from Dafydd

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